V0, jyg, ALICE week, March Preparing for the V0 TDR (Lyon-Mexico project)  The V0 detector in 3 chapters  1 - Tests and simulations of detection elements V0L and V0R design after tests in next August  2 - Photodetectors and Front End Electronics first plans and prototypes  3 - Simulations of the V0 responses (PPR contribution) efficiencies for minimum bias triggers: p-p et Pb-Pb multiplicity indicator luminosity control background filter for central detector and dimuon  Conclusion

V0, jyg, ALICE week, March Chapter 1 - The V0 detector  V0 in both sides of the vertex  V0L at –3.5 meters -5.1 < η < < R < 44.5 cm  V0R at 0.9 meter on the front absorber 1.7 < η < < R < 33.6 cm

V0, jyg, ALICE week, March Ring V0LV0R η max /η min  max /  min η max /η min  max /  min 1-5.1/ / /3.42.6/ / / /2.93.8/ / / /2.56.3/ / / /2.19.4/ / / / /20.7 V0 segmentation  Arrays with 72 detectors according to 5 rings/12 sectors in the FMD acceptance, in the dimuon arm acceptance

V0, jyg, ALICE week, March V0 scintillator element  Elementary channel (ring i element) plastic scintillator (SC) wave length shifting fibers in grooves (WLS) clear optical fibers for light transport (CL) photomultiplier (PMT) electronics (FE) for: …. triggering (V0, V1, V2) …. charge and time numerizations (Q, T)

V0, jyg, ALICE week, March Setup A  Coupling of WLS fibers on one of the front flat edges of scintillating elements 1 cm thick scintillator from 8 to 2 WLS fibers 40 cm long

V0, jyg, ALICE week, March Setup B  Coupling of WLS fibers on the latteral flat edges of scintillating elements 1 cm thick scintillator 8 WLS fibers on each side 40 cm long

V0, jyg, ALICE week, March Tests in T10 and with cosmics  From the MIP through several V0 elements  Fast scintillator from BICRON (BC408) 425 nm maximum emission, 2.1 ns decay constant  Shifting fibers (Y11 from Kuraray) directly on PM XP nm maximum absorption, 476 nm maximum emission  Light yield as a function of: glue or no glue for fixing the fibers (BC600) (-35% difference) Al/Teflon envelope on scintillator (factor 2 gain compared to TiO 2 paint) no reflector on fiber ends (-30% loss compared to Al or Teflon)  Time resolution with threshold discriminator: as a function of elements as a function of the collected light

V0, jyg, ALICE week, March Light yield from setup A direct proportion  No fix ratio between the collected light and the number of fibers saturation when increasing fibers  Light yield dependence on element and number of WLS fibers more results from very close setup by Gerardo next talk

V0, jyg, ALICE week, March Light /  time from setup A p 1 /  N + p 2

V0, jyg, ALICE week, March Light /  time from setups A and B  Much more light with setup B better time resolution

V0, jyg, ALICE week, March Simulations  Simulation based on the LITRANI code (C++/ROOT program) generation and propagation of the optical photons from their emission point to detecting devices  Geometry and optical parameters of the V0 elements absorption, diffusion, scattering lengths reflection, diffusion coefficients  Light yield within the fiber acceptance in the direction of the PMT

V0, jyg, ALICE week, March Light yield from setup A  Data normalized on ring 4 element with 4 fibers  Good relative agreement between measures and calculations

V0, jyg, ALICE week, March Light map from setup A  Large inhomogeneity in the light production depends on the WLS fiber positions zones of inefficiency in the corners fiber positions inefficiency zones

V0, jyg, ALICE week, March Light map from setup B  Better uniformity with setup B extreme MIP light dispersion of a factor 2.5 minimum contribution maximum contribution

V0, jyg, ALICE week, March Light yield from setups A and B Ring Setup A (10 mm) Setup B (10 mm) Setup B (15 mm)  Setup A (8 fibers): light depends on the geometry (~factor 2)  Setup B: light yield independent of the geometry goes like the SC thickness

V0, jyg, ALICE week, March Plan  Test of quadrants in August 2003 in a real configuration (SC/WLS fibers/connector/CL fibers/PMT) …. in independent elements (setup B with 1 and 1.5 cm in thickness) …. and from one unique SC plate (similar to setup A) next talk with (x, y) measurement of tracks  Last options chosen for a final design included in the TDR in September 2003  Mechanical construction starting in 2004

V0, jyg, ALICE week, March V0R with setup B optical fibers absorber V0R

V0, jyg, ALICE week, March CERN Maquette 1:1 Si outer absorberSi inner T0R V0R

V0, jyg, ALICE week, March Chapter2 - PMT and FEE  PMT signal dynamics: for a dynamics of MIP’s (expected in Pb-Pb) and a 1 MIP efficiency > 97% (required for pp)  Signal picked up from anode and last dynode (A/D = 6) fast rise and decay times (pulses within 20 ns)) good linearity (minimum signal distorsion) low dark noise (minimum V0 auto-triggering)  Good candidates exist  Fast electronics providing 3 levels of trigger to the CTP one MB in pp and Pb-Pb: V0 trigger and TRD wake-up one central and one semi-central in Pb-Pb: V1 and V2 triggers  Signal dynamics numerization 1 to 1000 in charge (relatively to minimum threshold) 0 to 256 ns in time (relatively to the bunch clock)  Fast electronics providing 3 levels of trigger to the CTP one MB in pp and Pb-Pb: V0 trigger and TRD wake-up one central and one semi-central in Pb-Pb: V1 and V2 triggers  Signal dynamics numerization 1 to 1000 in charge (relatively to minimum threshold) 0 to 256 ns in time (relatively to the bunch clock)

V0, jyg, ALICE week, March PMT noise measurement  Threshold: 5 p.e. V0 self-triggering XP2020: 20 c/s XP2972, R7400P: … c/s 5 1 from NA49 400

V0, jyg, ALICE week, March Electronics diagram CTP digitization MB trigger scintillator centrality triggers CTP

V0, jyg, ALICE week, March Integration in ALICE

V0, jyg, ALICE week, March Chapter 3 - Simulations  PYTHIA for pp extrapolated to proton beams of 7 TeV MB cross-section:  tot =  el +  inel = 101 mb  el = 22 mb and  inel = 79 mb each term will be measured by TOTEM at LHC energies  Limited covering of V0 at small angles (  max = -5.1 / 3.8) no detection of charged particles from elastic process  Luminosity: L = (N inel /eff inel )/  inel if PYTHIA is correctly calibrated (  inel ), we should be able to evaluate the term eff inel from simulations (within few %) … and counting N inel should allow to measure the luminosity  Two components for  inel =  SD +  NSD : SD: p + p > p + X (14 mb) NSD: p + p > X + Y (65 mb)

V0, jyg, ALICE week, March Triggering efficiency  pp multiplicity distribution in 4  white: Pythia without transport  Events with at least 1 MIP light grey: Pythia in vacuum light and dark grey: Pythia in AliRoot  Production of secondaries improves the triggering efficiency  eff inel = 84% from V0L*V0R

V0, jyg, ALICE week, March Efficiency function  Triggering efficiency as a function of the minimum number of left/right cells required for the coincidence V0L*V0R  If N cell cut = 1 for L and R eff inel from Pythia + AliRoot: (0.53 x x 65) / 79 = 0.86  Threshold could be necessary to kill residual p-gas background in the trigger rate  Simulations to evaluate the p-gas contribution are in progress SD NSD

V0, jyg, ALICE week, March Efficiency values eff inel N cut on Left cells N cut on Right cells

V0, jyg, ALICE week, March Multiplicity in pp  Multiplicity from Pythia + AliRoot 1000 events Signal in clear Signal + background in dark  Many secondaries due to the setup big effects in rings 1 left/right

V0, jyg, ALICE week, March Multiplicity in Pb-Pb  Multiplicity from Hijing + AliRoot 30 events with b = fm  Line = pure signal  Points = signal + background circle: V0L square: V0R  Many secondaries due to the setup big effects in rings 1 left/right

V0, jyg, ALICE week, March Background from AliRoot  S/B as a function of  (ring) B > 2S Background in V0R

V0, jyg, ALICE week, March Vertex distribution  Reconstructed tracks 1000 pp events  Important in V0R from ITS support, bellows and flange Background in V0R

V0, jyg, ALICE week, March Conclusion  Three chapters for the V0 in the TDR: detector (design and performances in September 2003) front end electronics (design and first tests by August) simulations (present and close future results)